|Tasmanian Sea Eagle (Haliateets leucogaster)|
Image courtesy of John Redeker, Tas
I went to a remote beach this week where you could usually count on seeing the odd Sea Eagle, yet there wasn’t a single one to be seen. When I came home and started to read about them, I was shocked to find that 52% of the world’s Raptors are in decline and around 18% of them are facing extinction, even in Australia and Tasmania. (Hint: The shorter version at Birdlife.org is easier to read). Half of Australia’s 35 native Raptor species are either endangered or listed because they are already extremely rare. In Tasmania, which has 13 species, there are now only around 100 breeding pairs of the mighty Wedge Tailed Eagle, 110 pairs of Grey Goshawks and 200 pairs of White Bellied Sea Eagles.
So what are Raptors and why is this happening?
Raptors are birds of prey, meaning that they hunt small game and eat meat or carrion. They include eagles, vultures, hawks, falcons and owls. Unfortunately, the most species - rich regions such as South and South East Asia and around the tropics in South America and sub-Saharan Africa, are not only experiencing the most rapid decline, but are the least studied. There are thus few baselines for determining trends and Raptors are anyway difficult to study as their numbers are generally small, their range is large and some are migratory as well. Still, it is the more static forest dwellers which continue to be most at risk.
Poisoning, accidental, secondary or otherwise is another all too common threat. When the veterinary drug diclofenac was introduced for use on cattle on the Indian sub -Continent in the 1990s, it lost 99% of four species of Old World Vultures in less than a decade. Fortunately, once the drug was banned, the vultures began to recover, but three years ago the same drug was approved for veterinary use in Spain, Italy and Portugal. There are now urgent calls to ban it in Europe as well. Some poisons used to control pests also end up killing the Raptors either directly, or because they feed upon the dead carcasses. Oiling, entanglement, pollution and road accidents are additional concerns. Because Raptors are scavengers, they are often killed themselves while consuming road kill. Lead poisoning from ingested shot is yet another not infrequent cause of death.
|Approximately 500 Bald Eagles are killed in the USA each year through contact with power lines, turbines and communications towers|
-Image courtesy of Jean Beaufort under CC licence
A more recent cause is the proliferation of electricity pylons, cell towers and windfarms. Although many birds are electrocuted or injured through contact with these - according to one US study, 214,000 -368,00 birds are killed by windfarms, 6.8 million by communications towers, and 3.7 billion by cats, but Raptors still tend to be overrepresented. This is because Raptors prefer high windy places where they can observe their prey, take advantage of wind currents and thermals and stay safe from predators. In the Catalan region near the French- Spanish border, electrocution was the main cause of death of the endangered Bonelli’s Eagle and also threatened the Spanish Imperial Eagle. Fortunately new protocols have recently been adopted by the UN to prevent or minimise such events. For example, in the case of pylons, better siting of towers, away from critical flightpaths and equipped with defensive mechanisms has resulted in 70% lower mortality, despite only 6% of the towers having been modified. With respect to windfarms, new turbine designs, deterrence and early warning systems using radar signals used by aircraft, are all showing promise. Still, compared to deaths from other causes such as domestic cats, deaths from windfarms are miniscule and may in the long run reduce deaths due to climate change and pollution.
Climate change presents a new threat to Raptors. According to a 2014 report by the Audubon Society hundreds of birds in the USA, are ‘at serious risk from climate change, with the Bald Eagle potentially losing up to 75% of its range.' At this stage there is little data on the likely effects in other regions, but preliminary studies with respect to the Tawny Eagle in the Kalahari Desert indicate that grassland and savannah dwellers will be especially vulnerable. While some species may be able to move further north (or south) as food and or water sources diminish, this has implications for our protected areas which have thus far proven to be one of the more successful strategies in terms of Raptor preservation.
Why it matters
Apart from their intrinsic value, the loss of these awesome creatures has implications for the survival of humans too.
In the first instance, Raptors may be the very large canaries in the coal mine that is our earth. Being at the top of their food chain, they accumulate environmental toxins much more quickly than other species, as was observed in the 1950s by Rachel Carson when she first noticed the decline of Bald Eagles as a consequence of cumulative poisoning by DDT, long before such effects were noticeable in humans.
Secondly, their absence may impact directly on humans in other ways. Since they are uniquely adapted to neutralising pathogens in the diseased and dead creatures they scavenge, they remove these from our environment too. Lesser scavengers, such as dogs and rats are unable to do this and not only contract more diseases themselves, but are more likely to pass them on to humans. Once the Old World Vultures were gone in India and Nepal, the population of feral dogs exploded, leading indirectly to disease outbreaks in humans, especially rabies. Could it be that our own recent seagull explosion where it was found that they were now carrying antibiotic resistant superbugs, is in fact a reflection of this process when top predators are lost?
Raptors are often the keynote species in their ecosystem and their removal can trigger catastrophic knock – on effects in other parts of the system. Wedge Tailed Eagles for example, keep other species in check, so that they do not become pests or deplete the available food supply. Young Raptors, not yet skilled enough for the hunt, tend to eat insects, thereby keeping those populations down. Along with birds in general Raptors also perform a number of other ecological services such as distribution of nutrients and seeds. The Wedge Tailed Eagle itself does not breed in poor seasons.
Next time we'll consider some ways in which we can help to ensure that Raptors will be around for future generations. Meanwhile, I apologise in advance that there are so few pictures. My bird photography has always been cringeworthy!